cmd/5a, cmd/6a, cmd/8a, cmd/9a: check nerrors before exit

Also fix one unaligned stack size for nacl that is caught
by this change.

Fixes #9539.

Change-Id: Ib696a573d3f1f9bac7724f3a719aab65a11e04d3
Reviewed-on: https://go-review.googlesource.com/2600Reviewed-by: Keith Randall <khr@golang.org>

src/cmd/5a/lex.c

@@ -122,6 +122,8 @@ main(int argc, char *argv[])
 	if(assemble(argv[0]))
 		errorexit();
 	Bflush(&bstdout);
+	if(nerrors > 0)
+		errorexit();
 	exits(0);
 }
 

src/cmd/6a/lex.c

@@ -132,6 +132,8 @@ main(int argc, char *argv[])
 	if(assemble(argv[0]))
 		errorexit();
 	Bflush(&bstdout);
+	if(nerrors > 0)
+		errorexit();
 	exits(0);
 }
 

src/cmd/8a/lex.c

@@ -127,6 +127,8 @@ main(int argc, char *argv[])
 	if(assemble(argv[0]))
 		errorexit();
 	Bflush(&bstdout);
+	if(nerrors > 0)
+		errorexit();
 	exits(0);
 }
 

src/cmd/9a/lex.c

@@ -131,6 +131,8 @@ main(int argc, char *argv[])
 	if(assemble(argv[0]))
 		errorexit();
 	Bflush(&bstdout);
+	if(nerrors > 0)
+		errorexit();
 	exits(0);
 }
 

src/runtime/asm_amd64p32.s

@@ -645,7 +645,7 @@ TEXT runtime·cputicks(SB),NOSPLIT,$0-0
 // memhash_varlen(p unsafe.Pointer, h seed) uintptr
 // redirects to memhash(p, h, size) using the size
 // stored in the closure.
-TEXT runtime·memhash_varlen(SB),NOSPLIT,$20-12
+TEXT runtime·memhash_varlen(SB),NOSPLIT,$24-12
 	GO_ARGS
 	NO_LOCAL_POINTERS
 	MOVL	p+0(FP), AX